A measure of near‐surface fluid motions that predicts air‐water gas transfer in a wide range of conditions

Turney, Damon E.; Smith, Walter C.; Banerjee, Sanjoy

doi:10.1029/2004gl021671

Cited by 45 publications

(58 citation statements)

References 26 publications

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“…Moreover, the study of Banerjee et al (2004) found that the surface divergence model can be applied to sheared free surfaces, which is supported by the simulations of Lakehal et al (2008a) and Lakehal, Fulgosi & Yadigaroglu (2008b). This observation is also verified in the experimental work of Turney, Smith & Banerjee (2005) with A being 0.45 and in the recent numerical simulation of Hasegawa & Kasagi (2009) with A being 0.40 for Sc of 1 and 100.…”

Section: Results Overview and Validationsupporting

confidence: 69%

Statistics of surface renewal of passive scalars in free-surface turbulence

et al. 2011

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We perform direct numerical simulation to study the transport of gas and heat as passive scalars in free-surface turbulence. Our analysis focuses on the surface age of surface fluid particles, i.e. the time elapsed since the last surface renewal they experienced. Using Lagrangian tracing of fluid particles combined with heat diffusion analysis, we are able to directly quantify surface age to illustrate scalar characteristics at different stages of interfacial transfer. Results show that at the early stage of surface renewal, vertical advection associated with upwellings greatly enhances surface gas flux; random surface renewal model does not apply at this stage when most of the interfacial gas transfer occurs. After a fluid particle leaves the upwelling region, it may enter a nearby downwelling region immediately, where the gas flux is sharply reduced but the variation in surface temperature is small; alternatively, the fluid particle may travel along the surface for some time before it is absorbed by a downwelling, where the surface temperature has changed significantly due to long duration of diffusion and the gas flux is also reduced. To gain further insight into the relationships between surface velocity and scalar quantities, we perform a statistical analysis of upwellings using clustering and nonlinear regression. With this analysis, we are able to provide qualitative and quantitative descriptions of the skewed probability density functions associated with the surface divergence, temperature and gas flux that support our physics-based investigation of surface renewal and surface age.

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Section: Results Overview and Validationsupporting

confidence: 69%

Statistics of surface renewal of passive scalars in free-surface turbulence

et al. 2011

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“…KG04; Turney et al 2005) and numerical studies (e.g. Handler et al 2003;Shen et al 2004;Magnaudet & Calmet 2006;Khakpour et al 2011) have confirmed that the surface divergence is a good measure for the transfer velocity as the surface condition is implicitly taken into account.…”

Section: Significant Reduction Of K Lmentioning

confidence: 90%

Isotropic-turbulence-induced mass transfer across a severely contaminated water surface

Herlina

Wissink

2016

J. Fluid Mech.

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Direct numerical simulations were performed to investigate the effect of severe contamination on interfacial gas transfer in the presence of isotropic turbulence diffusing from below. A no-slip boundary condition was employed at the interface to model the severe contamination effect. The influence of both Schmidt number (Sc) and turbulent Reynolds number (R T ) on the transfer velocity (K L ) was studied. In the range from Sc = 2 up to Sc = 500 it was found that K L ∝ Sc −2/3 , which is in agreement with predictions based on solid-liquid transport models, see e.g. Davies (1972, Turbulence Phenomena, Academic). For similar R T , the transfer velocity was observed to reduce significantly compared with the free-slip conditions. The reduction becomes more pronounced with increasing Schmidt number. Similar to the observation for free-slip conditions made by Theofanous et al. (Intl J. Heat Mass Transfer, vol. 19 (6), 1976, pp. 613-624), the normalized K L in the present no-slip case was also found to depend on R −1/2 T and R −1/4 T for small and large turbulent Reynolds numbers, respectively.

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“…Osborne (1965) presented a theory to describe the modulation of the skin temperature by waves and other flows that generate a straining flow in the skin layer. Surface straining models have also been used to describe the heat and gas transfer due to subsurface turbulence, by parameterizing the straining flow generated by turbulent eddies (e.g., Fortescue and Pearson 1967;McKenna and McGillis 2004;Turney et al 2005). A surface straining model was also applied by Csanady (1990) to predict the gas transfer due to high vorticity wavelets.…”

Section: Introductionmentioning

confidence: 99%

Variations in Ocean Surface Temperature due to Near-Surface Flow: Straining the Cool Skin Layer

Wells

Cenedese

Farrar

et al. 2009

Journal of Physical Oceanography

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The aqueous thermal boundary layer near to the ocean surface, or skin layer, has thickness O(1 mm) and plays an important role in controlling the exchange of heat between the atmosphere and the ocean. Theoretical arguments and experimental measurements are used to investigate the dynamics of the skin layer under the influence of an upwelling flow, which is imposed in addition to free convection below a cooled water surface. Previous theories of straining flow in the skin layer are considered and a simple extension of a surface straining model is posed to describe the combination of turbulence and an upwelling flow. An additional theory is also proposed, conceptually based on the buoyancy-driven instability of a laminar straining flow cooled from above. In all three theories considered two distinct regimes are observed for different values of the Pé clet number, which characterizes the ratio of advection to diffusion within the skin layer. For large Pé clet numbers, the upwelling flow dominates and increases the free surface temperature, or skin temperature, to follow the scaling expected for a laminar straining flow. For small Pé clet numbers, it is shown that any flow that is steady or varies over long time scales produces only a small change in skin temperature by direct straining of the skin layer. Experimental measurements demonstrate that a strong upwelling flow increases the skin temperature and suggest that the mean change in skin temperature with Pé clet number is consistent with the theoretical trends for large Pé clet number flow. However, all of the models considered consistently underpredict the measured skin temperature, both with and without an upwelling flow, possibly a result of surfactant effects not included in the models.

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A measure of near‐surface fluid motions that predicts air‐water gas transfer in a wide range of conditions

Abstract: A measure of near-surface fluid motions that predicts air-water gas transfer in a wide range of conditions Conceptual Model 75[4] The gas transfer coefficient, k, is defined as and convective liquid motions control the gas transfer rate.

Cited by 45 publications

References 26 publications

Statistics of surface renewal of passive scalars in free-surface turbulence

Statistics of surface renewal of passive scalars in free-surface turbulence

Isotropic-turbulence-induced mass transfer across a severely contaminated water surface

Variations in Ocean Surface Temperature due to Near-Surface Flow: Straining the Cool Skin Layer

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